Abstract 168: Coated-Platelets Improve TIA/Stroke Prediction in Asymptomatic Internal Carotid Artery Stenosis

Abstract

Background: Coated-platelets, a subset of procoagulant platelets observed upon dual agonist stimulation with collagen and thrombin, support a robust prothrombinase activity and provide a unique measure of platelet thrombotic potential. Coated-platelet levels are increased in large artery stroke compared to controls, and higher levels are associated with early stroke recurrence. We now examine whether coated-platelet levels predict TIA/stroke in asymptomatic internal carotid artery (ICA) stenosis. Methods: Consecutive patients referred for carotid Doppler evaluation were enrolled. Those taking anticoagulants, with dementia, or TIA/stroke within 6 months before enrollment were excluded. Coated-platelets were determined at baseline and reported as percent of cells converted to coated-platelets. Subjects were followed for up to 3 years for TIA/stroke. A receiver operating characteristic curve (ROC) analysis was conducted to compare performance of two models in predicting incident TIA/stroke. The first model included stenosis severity (<70% or ≥70%) while the second model included stenosis severity (<50% or ≥50%) and coated-platelet level as predictors. Results: We enrolled 343 patients. Follow-up ranged from 4 days to 39.7 months (mean 10.6 months). Fourteen TIA/strokes were observed. Ten were carotid-related. ROC analysis showed significant improvement in the predictive ability of the stenosis (≥50%) plus coated-platelets model compared to the stenosis (≥70%) only model (AUC: 0.88 ± 0.05 versus 0.71 ± 0.08, respectively; p=0.05). A cut-off of 46.5% for coated-platelet levels in combination with stenosis ≥50% yielded a sensitivity of 0.70 (0.42-0.98; 95% CI), specificity of 0.91 (0.88-0.94), positive predictive value of 0.18 (0.06-0.31), and a negative predictive value of 0.99 (0.98-1.0). Coated-platelet levels at 6 months did not significantly differ from baseline (p=0.69). Conclusions: Coated-platelet levels identify asymptomatic ICA stenosis patients at low risk for carotid-related stroke, which suggests a role for coated-platelets in risk stratification prior to revascularization.